This Task Order is for the completion of a Phase I clinical trial to test wherher Nestorone gel (progestogen) in addition to testosterone (T) gel (androgen), both applied transdermally, will suppress gonadotropins and sperm production. Preliminary results from an earlier study indicated that a dose of 8 mg of Nestorone gel was required in order to suppress gonadotropins sufficiently to a level that may produce inhibition of spermatogenesis however the duration of these preliminary studies was too short to evaluate if the degree of gonadotropin suppression was complete or sufficient to inhibit spermatogenesis. However, the results of the various doses allowed the selection of the appropriate dose for comparison to evaluate the safety and suppression of gonadotropins over a longer period of time. If a combination Nestorone and T gel regimen was effective, the NICHD proposed to conduct a larger study to evaluate the Nestorone gel dose combined with T gel using sperm production as a primary endpoint.